This invention relates to a continuous process for the manufacture of a new and improved cannula needle. The needle is adapted for use with a catheter which is passed therethrough for insertion into a patient. The needle is then withdrawn from the patient and separated from about the catheter that remains in place.
A very large number of patients are treated in this fashion throughout the world. It would be highly desirable to manufacture a reliable and inexpensive cannula needle at high production rates to accommodate typical catheters used in these treatments. Preferably, there is desired a one-piece cannula needle that can be readily manipulated for insertion into a patient and then be easily broken apart and separated from about the catheter.
One type of guide needle for a catheter is disclosed in U.S. Pat. No. 3,359,978 to Raymond M. Smith. That needle is manufactured from steel flat stock that has been stamped in a one-shot operation to form a needle pattern, reinforcing roof and handles or wings. A groove or trough is formed in the flat stock during the stamping operation, and the flat stock is then rolled to a circular needle configuration. In use, the handles are flexed to open the needle, and the open needle is then separated from the catheter. Alternatively, flat sheet stock is formed into a tube, and two grooves are milled on the tube exterior. In use, the handles are flexed to split open the needle along the upper groove, while the lower groove functions as a hinge; the needle is then separated from about the catheter.
While the Smith needle is simple and inexpensive, it has not been commercialized. The problem arises because it is extremely difficult to manufacture a single groove of uniform depth using a stamping operation. This type of groove impairs a uniform and controlled opening of the needle. Alternatively, if two grooves are machined on a tube, the upper groove must be sufficiently deep to split open easily, and the lower groove must be deep enough to permit hinge flexing, but not too deep to avoid premature splitting.
Consequently, in both cases when the needle is flexed open, there is an excessive variation in the opening or flex properties between needle batches and even between individual needles, and this variation is unacceptable to the user, generally a nurse.
There is desired a cannula needle for use with a catheter, the cannula being continuously grooved and formed from flat sheet metal stock, rolled, and then cut into a needle configuration. The groove should be sufficiently deep so that when flexed open, the needle will easily split away from the catheter in a uniform manner and usually in a single motion. Conventional means preferably should be used to form the groove continuously such as by cold rolling, cutting with a diamond, etc.
To facilitate working of the metal stock into a grooved, rolled and cut form, the flexing wings must be attached to the needle in a separate operation, and this may be done by laser or resistance welding, etc. A form of laser welding is described in U.S. Pat. No. 4,100,393 to Ronald B. Luther.